Diverticulosis Without Inflammation Is Unlikely the Primary Pain Source; Consider L5 Pars Defect and Repeat Imaging with Contrast
The presence of diverticula without inflammation on non-contrast imaging does not explain left-sided pain, and the bilateral L5 pars defect is a more plausible pain generator that warrants further evaluation. The non-contrast study significantly limits diagnostic accuracy for detecting inflammatory processes.
Why Diverticula Alone Don't Cause Pain
Diverticulosis (the mere presence of diverticula) is asymptomatic in the vast majority of patients—only 1-4% of patients with diverticulosis ever develop acute diverticulitis, which is the actual pain-causing condition 1, 2.
Diverticulitis is fundamentally an extramucosal inflammatory process that requires demonstration of pericolonic fat stranding, bowel wall thickening, or complications like abscess formation to be clinically significant 3.
The imaging showed "no inflammatory process," which effectively rules out acute diverticulitis as the pain source 3.
Non-contrast CT has severely limited sensitivity for detecting the inflammatory changes that define diverticulitis—contrast enhancement is essential for identifying pericolonic inflammation, abscess formation, and bowel wall thickening 3.
The L5 Pars Defect as Pain Generator
Bilateral L5 pars defects (spondylolysis) are a well-established cause of low back pain, particularly in younger patients and those with history of high-impact sports 4.
Pars defects can cause pain through mechanical instability, and if left untreated may progress to spondylolisthesis with dynamic canal stenosis and radiculopathy 4.
The anatomical location of L5 pars defects can produce referred pain to the left lower quadrant/flank region, making this a plausible explanation for the patient's symptoms 5.
Pain from pars defects is typically mechanical—worse with extension, twisting, or prolonged standing 4.
Critical Imaging Limitation
The decision to perform imaging without contrast due to patient request has severely compromised diagnostic accuracy 3.
CT with IV and oral contrast is the gold standard for evaluating left lower quadrant pain, with sensitivity and specificity approaching 98-100% for diverticulitis when properly performed 3, 1.
Non-contrast imaging cannot adequately assess for bowel wall enhancement, pericolonic inflammation, or early abscess formation 3.
Recommended Next Steps
Strongly counsel the patient on the necessity of contrast-enhanced CT to definitively exclude diverticulitis and other inflammatory processes—the benefits far outweigh the minimal risks in most patients 3.
If contrast CT remains refused and clinical suspicion for diverticulitis persists, MRI abdomen/pelvis with gadolinium is an alternative with 86-94% sensitivity and 88-92% specificity for inflammatory conditions, though it may miss small amounts of extraluminal air 3, 6.
Evaluate the L5 pars defect with dedicated lumbar spine imaging—thin-section CT with reverse gantry angle or SPECT bone scan can assess for active stress reaction versus chronic defect 5.
Consider plain radiographs including coned lateral view of lumbosacral junction and AP view with 30-degree cranial angulation to better characterize the pars defect 5.
Clinical Assessment Priorities
Assess for mechanical back pain patterns: pain worse with extension, twisting, or prolonged standing suggests pars defect as source 4.
Assess for diverticulitis red flags: fever, inability to pass gas/stool, severe tenderness with guarding, vomiting, bloody stools, or leukocytosis mandate immediate evaluation regardless of imaging 6, 7.
Check inflammatory markers (CBC, CRP) to assess for occult inflammation not visible on non-contrast imaging 7.
If pain is related to bowel movements or dietary triggers, consider functional bowel disorders once structural pathology is definitively excluded with proper imaging 6.
Common Pitfall to Avoid
- Do not attribute pain to incidental diverticulosis—this is one of the most common diagnostic errors in evaluating left-sided abdominal pain 3. The diverticula are likely incidental findings unrelated to the current symptoms unless inflammation is demonstrated.